1. Field
This disclosure relates generally to radio, and more specifically, to a radio receiver having an ignition noise detector and method therefore.
2. Related Art
Automobile engines generate ignition noise that can be picked by radio receivers. The ignition noise is typically in the form of broadband spikes that cause audible effects that can be heard on the radio speakers. A noise blanker is included in radios to reduce the effects of ignition noise. When a received RF (radio frequency) signal is relatively strong, ignition noise effects are negligible.
Typically noise blankers inherently do some harm to audio quality or fidelity of an audio signal. Therefore, noise blankers should only operate when the harm done is offset by the need to remove the noise spike. A noise detector is used to detect the noise and enable the noise blanker for the time when noise is detected.
Ignition noise has relatively strong energy in a frequency band of about 10 KHz (kilohertz) to about 30 KHz (ultra-sonic band). Thus, ignition noise detection can be accomplished by monitoring this frequency band and the detected ignition noise can be removed using a noise blanker. However, non-ideal radio channel effects will affect the performance of an AM noise blanker, such as adjacent interference, multipath echo, etc. The non-ideal channel effects can cause falsing problems, where the false indication of ignition noise enables the noise blanker when there is no noise present. For example, when a strong adjacent AM station exists within about 10 KHz or 20 KHz away, the adjacent energy could interfere with the ignition noise detector and cause the noise detector to enable the noise blanker, thus distorting the audio signal unnecessarily.
Therefore, it would be desirable to have a radio receiver that removes ignition noise spikes without affecting the fidelity of the audio signal unnecessarily.